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Highlights of 2016 ASCO Genitourinary Cancers Symposium

The 2016 Genitourinary Cancers Symposium will kick off this coming Thursday in San Francisco. At a pre-meeting press cast, investigators were enthusiastic about the meeting, which will focus on "patient-centric" care. They spoke about 3 separate studies: two related to prostate cancer and one in advanced kidney cancer.

Another Benefit of Aspirin?

[Abstract 306]

Regular use of aspirin appears to lower the risk of developing and dying from lethal prostate cancer, according to a large observational study. Regular aspirin use did not, however, lead to a reduction in the overall incidence of prostate cancer.

Lead study author, Christopher Brian Allard, MD, Urologic Oncology Fellow at Brigham and Women's Hospital and Massachusetts General Hospital in Boston said: "It is premature to recommend aspirin to prevent lethal prostate cancer, but men with prostate cancer who may already benefit from aspirin's cardiovascular effects could have one more reason to consider regular aspirin use." He added that discussions with patients about aspirin should include bleeding risks versus benefits.

Previous studies of aspirin and prostate cancer have been equivocal. Dr. Allard said his is the first study to focus specifically on prevention of lethal prostate cancer and to clarify the potential role of aspirin in prevention of advanced disease.

The study was based on data from 22,071 men enrolled in the Physician's Health Study. Over 27 years of follow up, 3193 men were diagnosed with prostate cancer and 403 developed lethal prostate cancer, defined as metastatic disease or prostate cancer-specific death. Regular aspirin use was defined as 3 or more tablets per week (of any dosage).

A multivariate analysis adjusted for age, race, body mass index, and smoking status showed that regular aspirin use was protective in the overall trial, resulting in a 24% reduced risk of developing lethal prostate cancer versus no regular aspirin use. Among men with a diagnosis of prostate cancer, regular aspirin use after diagnosis was associated with a 39% reduced risk of dying of prostate cancer.

Regular aspirin use did not protect against developing prostate cancer, high-grade prostate cancer, or locally-advanced prostate cancer.

Dr. Allard and colleagues will study mechanisms by which aspirin reduces the risk of prostate cancer death. More research is needed to select subsets of men that would benefit from regular aspirin use and to determine the optimal dose.

Sumanta Pal, MD, ASCO spokesperson and moderator of the presscast pointed out that there may be one more benefit of aspirin beyond that seen in colorectal cancer and cardiovascular disease. "....It's thought-provoking that this low-cost medication may lower the risk from prostate cancer," he said.

New Blood Test May Guide Treatment Decisions

(Abstract 163)

A preliminary study suggests that an experimental blood test based on a "liquid biopsy" may be useful for individualizing treatment decisions for men with advanced prostate cancer. The non-invasive assay scans a patient's blood for cancer cells (i.e., circulating tumor cells [CTC]), analyzing their shape and size as well as genetic makeup to predict whether patients can benefit from hormone-directed therapies such as abiraterone and enzalutamide

A "liquid biopsy" based on easily-obtained blood samples is much more convenient and comfortable for patients than invasive tumor biopsy. Also, this assay allows for earlier adjustments in therapy compared with an invasive tumor biopsy.

"Not all men respond equally to either enzalutamide or abiraterone, and some men don't respond at all. If this test is validated, it could be used to help select the treatment to which a patient is more likely to respond, sparing the toxicities that may result from an ineffective treatment," explained lead author Howard I. Scher, MD, chief of the Genitourinary Oncology Service at Memorial Sloan-Kettering Cancer Center in New York City.

For the test, a blood specimen is stained with dyes to distinguish normal blood cells from CTCs, and then the cells are scanned for morphology, "much like facial recognition software used at airport security," said Dr. Scher. "The software can quickly identify a cell by examining its features." The cells of interest can then be analyzed for genetic abnormalities.

In the study, 221 blood specimens were obtained from 179 patients with metastatic prostate cancer slated for treatment with either enzalutamide or abiraterone. Patients with a higher heterogeneity score (i.e., more variation in CTC appearance and genetic composition) had a poor response to hormone therapy. Compared with those with a low heterogeneity score, patients with high heterogeneity score had shorter median progression-free survival (5 months vs 17 months) and overall survival (9 months vs not yet reached).

Heterogeneity score was not associated with response to taxane chemotherapy.

Before this assay can be used in clinical practice, it needs to be validated in larger sample sizes. Then clinical studies are required to determine if results predict outcomes.

"Tumors change over time, and prostate cancer appears to become especially complex over time. This exciting preliminary study suggests a method that may help us profile individual cancers in real time... Eventually, we may be able to offer the right treatment to the right patient and personalize our selection of therapy," said Dr. Pal.

Cabozantinib Beats Everolimus in Advanced Kidney Cancer

(Abstract 499)

Cabozantinib achieved greater benefit than everolimus, the standard of care, in patients with previously treated advanced kidney cancer, according to an updated analysis of the phase III METEOR trial. Results showed that progression-free survival (PFS) was significantly improved with cabozantinib across all subgroups. Cabozantinib's superiority was independent of risk category, metastatic sites, and number and types of prior treatments.

An interesting hypothesis-generating finding was that patients who failed on second-line checkpoint inhibitor therapy did especially well on cabozantinib versus everolimus. But this included only a small number of patients (n=32) and needs further study.

Although current treatments can help patients with advanced kidney cancer, more effective treatments are needed, according to lead study author Bernard Escudier, MD, Institut Gustave Roussy, Villejuif, France. "Our preliminary results suggest that cabozantinib may help overcome treatment resistance and provide new hope for patients with this aggressive cancer," he said.

Cabozantinib is approved for the treatment of thyroid cancer and is investigational in kidney cancer.

The study randomized 658 patients with advanced kidney cancer previously treatment with VEGFR inhibitor therapy (and 32 with previous immunotherapy) to receive cabozantinib or everolimus. Analysis of the first 375 patients found that cabozantinib improved median PFS versus everolimus: 7.4 months versus 3.8 months, respectively.

At the GU Cancers Symposium, Dr. Escudier will present results on all 658 patients enrolled in the trial, which basically replicate the findings in the first 375 patients, with a 48% reduction in risk of progression for those treated with cabozantinib versus everolimus.

Final overall survival results are expected to be presented at ASCO 2016.

An exploratory subgroup analysis found that cabozantinib was especially effective in patients with bone metastasis (considered difficult to treat), patients previously on sunitinib, and those who failed on prior checkpoint inhibitor therapy.

Common side effects with cabozantinib included diarrhea, fatigue, nausea and vomiting, decreased appetite, and hand-foot syndrome; the most common side effects with everolimus were fatigue, anemia, decreased appetite, cough, and dispend.

"These results exceed what we have seen in this setting. Virtually all patients derive benefit from cabozantinib. These striking early signs of success exemplify how precision medicine is paying off for patents," said Dr. Pal.

By Alice Goodman

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